Mechanical ventilation is frequently used in the operating room and the intensive care settings. Although essential in many cases, mechanical ventilation can be responsible for ventilator-induced lung injury (VILI). The relationship between mechanical ventilation and VILI has been clearly demonstrated in animals and is highly suspected in humans. The putative mechanism responsible for VILI is excessive pulmonary strain or overdistension. Frequently observed in mechanically ventilated patients, the presence of a severe pre-existing pulmonary disease can increase the risk of overdistension. The development of a tool allowing early detection of pulmonary overdistension would represent a great asset in the prevention of VILI by allowing safer adjustments of mechanical ventilation parameters. Ultrasonographic imaging is a non-radiant, non-invasive technique already available in the intensive care setting. Already used for cardiac strain measurements, ultrasonography is a promising avenue to assess pulmonary strain.This study will aim to establish normal pleural strain values using ultrasonography in healthy volunteers. Purpose: The primary objective is to calculate 95% confidence intervals in pleural strain for a set of 8 inspired volumes at 15 predetermined lung areas in healthy volunteers. The secondary objectives of the study are: * to modelize the relation between pleural strain and inspired volume * to modelize the relation between pleural strain and global pulmonary volumetric strain * to modelize the relation between pleural strain and maximal echo intensity change * to compare the regional distribution pattern of pleural strain in healthy volunteers in dependent versus non-dependent areas. Hypothesis: Elastography using the Lagrangian speckle model estimator based on optical flow allows the determination of normal mean values and 95% confidence intervals of pleural strain (average Von Mises coefficient) in 15 predetermined lung areas for a set of 8 inspired volumes in healthy volunteers.
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Average Von Mises
Timeframe: At the end of the study on Day 1